This invention relates to a liquid-pervious topsheet for disposable absorbent articles such as disposable diapers and menstruation pads and a process for making the same.
Japanese Patent Application Disclosure No. 1995-328061 describes a liquid-pervious topsheet used in a disposable body fluids absorbent article, particularly, a menstruation pad comprising a nonwoven fabric and a liquid-impervious thermoplastic film. The plastic film is provided in the form of a plurality of film strips extending parallel one to another at predetermined intervals and bonded to the upper surface of the nonwoven fabric. The nonwoven fabric is formed with high density regions covered with the plastic film and with low density regions exposed between each pair of adjacent film strips. With such a topsheet, menstrual fluids discharged on the upper surface of the topsheet permeate the low density regions exposed between each pair of adjacent film strips into a core underlying the topsheet. The core has its upper side entirely covered with the nonwoven fabric and partially covered with the film strips so that the core soiled with menstrual fluids is not visually inconspicuous. An amount of menstrual fluids once discharged on the low density region tends to transfer to the high density regions and, as a result, the high density regions contain a relatively large amount of menstrual fluids. In spite of the large amount of menstrual fluids possibly contained in the high density regions, soil due to this is inconspicuous since the high density regions directly underlie the respective film strips. This known topsheet is claimed to alleviate a visual discomfort possibly experienced by a wearer of the article when the user disposes of the used article.
However, one of the problems associated with the forsaid conventional topsheet used in the menstruation pad is that, in the low density regions exposed between each pair of adjacent film strips, the portions of the core underlying the low density regions and soiled with menstrual fluids can be seen through the nonwoven fabric making the part of the topsheet.
Another problem associated with the foresaid conventional topsheet is that, if the topsheet rubs a wearer""s skin transversely of the direction in which the film strips extend as the wearer s body moves, edges of the respective film strips may irritate the wearer""s skin as knife edges.
It is an object of this invention to provide a topsheet for a body fluids absorbent article that allows a soiled with body fluids to be concealed over a large range and simultaneously provides a smooth and velvet touch.
The object set forth above is achieved by a first aspect of this invention relating to a liquid-pervious topsheet used in body fluids absorbent article, and by second to fourth aspects of this invention relating to a process for making such a liquid-pervious topsheet.
According to the first aspect of this invention, there is provided liquid-pervious topsheet for a body fluids absorbent article comprising a first plastic film layer forming an upper surface of the topsheet, a second plastic film layer forming a lower surface of the topsheet and a fibrous assembly layer disposed between the first and second plastic film layers and bonded to the first and second plastic film layers, wherein:
the first plastic film layer includes a plurality of first plane regions spaced one from another and extending in parallel one to another in one direction and the second plastic film layer includes a plurality of second plane regions spaced one from another and extending in parallel one to another in the one direction wherein each of the first and second plane regions has a thickness of 0.001xcx9c0.05 mm and a width of 0.03xcx9c1 mm and wherein, of each pair of the first plane regions adjacent to each other and each pair of the second plane regions adjacent to each other, at least each pair of the first plane regions adjacent to each other are connected with each other by a plurality of bridge-like regions extending between the plane regions adjacent to each other;
of the first and second plane regions, at least the first plane regions are formed along edges thereof with first rising regions extending upward from an upper surface of the first plane regions in an irregular array of substantially triangular tooth;
the second plastic film layer partially underlies regions of the fibrous assembly layer defined between a lower surface of each pair of the first plane regions adjacent to each other; and
the fibrous assembly layer is bonded between the first plane regions and an upper surface of the second plane regions, and contains of hydrophilic fiber of 5 wt % or higher.
According to the second aspect of this invention, there is provided a process for making a liquid-pervious topsheet for a body fluids absorbent article comprising the steps of:
a. continuously feeding a composite web comprising a plastic film and a fibrous assembly underlying the plastic film and bonded to a lower surface of the plastic film in one direction;
b. subjecting a lower surface of the continuously fed composite web to high pressure columnar water streams ejected from a plurality of nozzles arranged transversely of the web and thereby rupturing the plastic film by the high pressure columnar water streams in the one direction according to traces of the high pressure columnar water streams to form the plastic film with a plurality of first plane regions extending in parallel one to another in the one direction, a plurality of openings extending in parallel one to another in the one direction between each pair of the first plane regions adjacent to each other, a plurality of first rising regions extending from edges of the first plane regions defining the openings substantially in the same direction as the high pressure columnar water streams, in an irregular array of substantially triangular tooth, and a plurality of bridge-like regions extending across each of the openings to connect each pair of the first plane regions adjacent to each other; and
c. bonding a plurality of plastic film strips extending in parallel one to another in the one direction to a lower surface of the fibrous assembly so that the plastic film strips at least partially underlie portions of the fibrous assembly defined by each of the openings.
According the third aspect of this invention, there is provided a process for making a liquid-pervious topsheet for a body fluids absorbent article comprising the steps of:
a. continuously feeding a composite web comprising a plastic film and a fibrous assembly underlying the plastic film and bonded to a lower surface of the plastic film in one direction;
b. subjecting an upper surface of the continuously fed composite web to high pressure columnar water streams ejected from a plurality of nozzles arranged transversely of the web and thereby rupturing the plastic film by the high pressure columnar water streams in the one direction according to traces of the high pressure columnar water streams;
c. subjecting a lower surface of the composite web, substantially in accordance with the traces of the high pressure columnar water streams, to high pressure columnar water streams to form the plastic film with a plurality of first plane regions extending in parallel one to another in the one direction, a plurality of openings extending in parallel one to another in the one direction between each pair of the first plane regions adjacent to each other, a plurality of first rising regions extending from edges of the first plane regions defining the openings substantially in the same direction as the high pressure columnar water streams in an irregular array of substantially triangular tooth, and a plurality of bridge-like regions extending across each of the openings to connect each pair of the plane regions adjacent to each other; and
d. bonding a plurality of plastic film strips extending in parallel one to another in the one direction to a lower surface of the fibrous assembly so that the plastic film strips at least partially underlie portions of the fibrous assembly defined by each of the openings.
According to the fourth aspect of this invention, there is provided a process for making a liquid-pervious topsheet for a body fluids absorbent article comprising the steps of:
a. continuously feeding a composite web in one direction, the composite web comprising an upper plastic film, a lower plastic film and a fibrous assembly disposed between the upper and lower plastic films and bonded to a lower surface of the upper plastic film and to an upper surface of the lower plastic film in one direction; and
b. subjecting an upper surface of the continuously fed composite web to high pressure columnar water streams ejected from a plurality of nozzles arranged transversely of the web and thereby rupturing the upper and lower plastic films in according with traces of the high pressure columnar water streams in the one direction to form the upper and lower plastic films with a plurality of first plane regions extending in parallel one to another in the one direction, a plurality of openings extending in parallel one to another in the one direction between each pair of the first plane regions adjacent to each other, a plurality of first rising regions extending from edges of the first plane regions defining the openings substantially in the same direction as the high pressure columnar water streams in an irregular array of substantially triangular tooth, and a plurality of bridge-like regions extending across each of the openings to connect each pair of the plane regions adjacent to each other.